The field of the invention is that of forming a body contact in SOI integrated circuits.
The need for a body contact in SOI FETs is well known. Many schemes have been proposed to provide a conductive path to ground to draw holes away from the transistor body. A straightforward approach is to increase the active area within the isolation dielectric to provide room to place a contact on the surface and an implant below the surface to provide a low-resistance path from the body to the contact. Such an approach, of course, takes up valuable silicon area.
Additionally, as the silicon device layer becomes thinner, it becomes increasingly more difficult to contact the body without incurring a large series resistance in the traditional approach.
The invention relates to a body contact that employs a leaky p-n junction (diode) in one of the source and drain, so that a conductive path is formed from the body through the leaky p-n junction to the transistor terminal. The other p-n junction in the FET has standard properties, so that there is no excessive leakage through the transistor.
A feature of the invention is the use of a non-critical block mask for one or more leakage implants, together with an angled leakage implant that penetrates under the gate to deliver a higher concentration of leakage ions at the p-n junction.